The present invention relates to thermostatically controlled faucets and more particularly to thermostatic faucets operated by temperature responsive feedback controlled servomechanisms.
Since shortly after the time that hot and cold running water first became a common feature of architecture, there has been an awareness of the occasional inconvenience that can result from a sudden undesirable change in temperature or pressure of the pressurized water in either of the lines supplying water to a faucet. In some cases, the resulting chage in the temperature of the mixed outlet water can result in discomfort to the user of the faucet. The discomfort can be particularly pronounced when the valve is a shower mixing valve and the user is within the shower stall. A sudden pressure drop in the cold water line, such as that which frequently occurs when a toilet is flushed, will cause a sudden increase in the temperature of the shower water, requiring the user to move quickly away from the stream of water.
Several faucets and mixing valves have been developed in an attempt to reduce or eliminate this problem. They include valves provided with thermometers, thermostats or stop mechanisms. Each of these valve types is described below.
One design offered in the past as an attempt to ameliorate this problem is the provision of a thermometer in the escutcheon of the faucet to notify the user of the temperature of the water. An example of this type of faucet is disclosed in U.S. Pat. No. 3,960,016 (issued June 1, 1976). The thermometer will warn the user of gradual temperature changes or of changes that occur while the user is not in contact with the water but is of little use to protect the user from sudden pressure or temperature changes in the water supply line while the user is in contact with the water.
Another partial solution offered in the past is the provision of a selectively disengagable stop mechanism mounted to the escutcheon. The stop mechanism prevents the user from selecting a setting of the faucet control handle that exceeds some preselected ratio of hot water to cold water. Examples of this type of faucet are disclosed in U.S. Pat. No. 3,559,684 (issued Feb. 2, 1971) and U.S. Pat. No. 4,089,347 (issued May 16, 1978). The stop mechanism will prevent the user from selecting a setting that will produce outlet water above a predetermined temperature under normal circumstances. The stop mechanism will not prevent the outlet water from exceeding the predetermined maximum temperature when the pressure drops in the cold water line.
Five types of self-regulating valves have been designed to combine pressurized hot and cold water and to produce a more nearly constant temperature of water at an outlet. One type of self-regulating valve, typified by the valve disclosed in U.S. Pat. No. 2,308,127 (issued Jan. 12, 1943) uses a pressure balance mechanism to prevent the sudden temperature changes that arise from pressure changes in one of the supply lines. This type of valve will not, however, respond to a decrease in the temperature of water in the hot water supply line and will therefore not compensate for the more gradual temperature change that occurs as the hot water tank cools off due to peak household demand or recovers after the household demand is reduced.
Another type of self-regulating valve provides shut off mechanism that automatically stops or diverts the flow of the water discharged by the faucet when the temperature of the outlet water exceeds some preselected maximum temperture. An example of this type of valve is disclosed in U.S. Pat. No. 2,534,378 (issued Dec. 19, 1950).
A third type of self-regulating valve is the directly driven thermostatically controlled valve. These valves typically consist of a housing having a mixing chamber, a hot water input passageway, a cold water input passgeway and a proportioning valve between the input passageways and the mixing chamber. A temperature responsive element, disposed within the mixing chamber, is coupled directly to the proportioning valve. Examples of this type of valve are disclosed in U.S. Pat. No. 2,272,403 (issued June 10, 1939), U.S. Pat. No. 2,383,215 (issued July 26, 1943), U.S. Pat. No. 2,463,640 (issued Mar. 8, 1949), and U.S. Pat. No. 3,539,099 (issued Nov. 10, 1970).
It should be noted that the directly driven thermostatically controlled valves do not actually produce a constant outlet water temperature but, instead, greatly reduced the amount that the outlet water temperature will deviate from a preselected temperature when there are temperature or pressure changes in the water supply lines. This charcteristic can be best understood by examining the manner in which this type of valve functions. The user preselects a temperature by adjusting the position of the proportioning valve until the outlet water reaches a preselected temperature. If the temperatures and pressures of the water supplies are constant, the proportioning valve remains stationary and the outlet water maintains the preselected temperature. The dynamic system consisting of the temperature responsive mechanism connected in series with the proportioning valve will therefoe be in static equilibrium.
If, however, the pressure or the temperature of the water in one of the supply lines assumes a new constant value, the temperature of the mixed outlet water is temporarily changed. The temperature responsive mechanism responds to the temperature change by directly moving the proportioning valve in the direction that will tend to restore the mixed water temperature to its previous level. As the proportioning valve is moved, the mixed water temperature changes and, eventually, causes the temperature responsive mechanism to reverse the direction of its movement. After a period of oscilation, the dynamic system will seek a new equilibrium position corresponding to a new equilibrium outlet water temperature. This new equilibrium temperature is clearly not identical to the preselected temperature since the position of the temperature responsive mechanism corresponding to the preselected temperature is the initial position of the mechanism.
The fourth type of self-regulating valve that has been disclosed in the past is the feedback servomechanism valve. The feedback servomechanism type of valve uses a valving element that is not directly fastened to the temperature responsive element. When the temperature responsive element senses a deviation in temperature from a preselected temperature, a signal is transmitted to a valving element, causing it to move in the direction that will alter the temperature in the desired direction. When the valve has moved to the proper position to produce the desried temperature of outlet water, the temperature responsive element detects that the outlet water temperature is correct and ceases transmission of the signal to shift. Examples of this type of valve are disclosed in U.S. Pat. No. 1,869,663 (issued Aug. 2, 1932) U.S. Pat. No. 2,449,766 (issued Sept. 21, 1948), U.S. Pat. No. 2,542,273 (issued Feb. 20, 1951), U.S. Pat. No. 2,550,907 (issued May 1, 1951) and U.S. Pat. No. 3,561,481 (issued Feb. 9, 1971).
The servomechanism valves represent an improvement in theory over the directly driven valves because the temperature responsive element is almost always restored to the same equilibrium position when the preselected temperature is reached regardless of the temperature or the pressure of the supply water. Furthermore, since there is no balance required to reach an equilibrium position, similar to that associated with the directly driven thermostatically controlled valve, the servomechanism valves can respond more quickly to adjust the outlet water temperature. Therefore, the servomechanism thermostatic valve will more accurately maintain the preselected temperature than the directly driven thermostatic valve.
Unfortunately, however, most servomechanism valves do not respond in the theoretical fashion described above when there is an extreme pressure imbalance between the hot inlet water and the cold inlet water because the pressure imbalance alters the equilibrium position of the valve member. Furthermore, the previously designed servomechanism valves are extremely large in comparision to the size of conventional faucet valves. Installation of one of these valves requires complete replacement of the existing faucet or drasitc alteration of the existing faucet. Another major disadvantage which is common to servomechanism valves and two stage valve assemblies is that they have long narrow fluid passageways that are easily clogged by particles suspended in the supply water.
The fifth type of valve assembly that has been proposed is the two stage valve assembly. This valve assembly provides a first stage comprising a pressure equilization means to compensate for pressure changes by maintaining a constant ratio between the hot water pressure and cold water pressure. Downstream of the pressure equalization piston, the valve assembly provides a second stage comprising a thermostatically controlled proportioning valve. An example of this type of valve is found in U.S. Pat. No. 3,539,099 (issued Nov. 10, 1970). The major advantage of the two stage valve assembly is that the outlet water temperature remains selectively constant over a large range of pressures and temperatures in the supply lines. The major disadvantage of using a two stage valve assembly is that there is a substantial increase in the number of components, the cost of assembly, and the space required for the valve assembly as compared with one stage valves.
It would therefore be useful to provide a single stage valve that combines all the advantages of the previous valves but avoids their disadvantages. Such a valve should be compact and have comparatively few expensive components. It would produce a nearly isothermal output and would not be susceptible to failure due to the accumulation of particles along fluid passageways. It would shut off the outlet water when the preselected water temperature could not be achieved due to an absence of pressure in either the hot or the cold water supply line. It would provide an indication of the actual temperature of water that has been selected. It would provide selectively disengagable stop means to prevent inadvertent selection of an outlet water temperature in excess of some predetermined maximum hot water temperature. Furthermore, it would be easy to install.
A primary feature of the present invention is that it provides a reliable compact thermostatically controlled valve wherein all the valving elements and temperature sensing elements can be provided within a control handle. An advantage of this configuration is that a handle assembly may be adapted to be fitted to existing single handle faucet sockets. Another advantage of this configuration is that it permits easy access to internal valve components for servicing and repair. Another advantage of this configuration is that it permits the use of a temperature indicating element visible on the exterior of the handle to indicate the temperature of the mixed water being discharged by the valve. Still another advantage to this configuration is that it permits providing the control handle with a compact temperature preselection mechanism. Still another advantage to this configuration is that it permits providing the control handle with a selectively disengagable stop mechanism limiting the maximum hot water temperature setting to prevent the user from unintentionally preselecting a temperature greater than a predetermined maximum temperature.
Another feature of the present invention is that it provides a servomechanism valve having a movable proportioning valve which is not affected directly by changes in pressure in either of the supply lines, but instead is affected only by the temperature of the mixed water. The advantage to this design is that the valve will produce a more nearly isothermal output than previous servomechanism valves.
It is therefore one object of the present invention to provide a reliable thermostatically controlled valve using a feedback controlled servomechanism.
Another object of the present invention is to provide a compact thermostatically controlled valve that may be mounted within the control handle of a faucet.
A third object of the present invention is to provide a handle module which contains a thermostatic valve assembly and which may be easily adapted to be fitted to the socket of an existing single handled faucet, the module replacing the conrol handle and some adjacent hardware of the existing faucet.
Another object of the present invention is to provide a thermostatically controlled proportioning valve that will produce an isothermal output even under extreme variations in termperature and pressure in the supply lines.
Another object of the present invention is to provide a single handle faucet having a temperature indicator mounted to the handle.
Another object of the present invention is to provide a servomechanism valve assembly having long and narrow fluid passageways which valve assembly is not susceptible to failure due to the accumulation of particles along the passageways.
Still another object of the present invention is to provide a thermostatically controlled faucet having a selectively disengagable stop mechanism limiting the maximum hot water temperature setting.
Still another object of the present invention is to provide a thermostatically controlled faucet with a restore mechanism to reset the thermostat to a temperture at or below a predetermined maximum level when the faucet is not in operation.
Still another object of the present invention is to provide a faucet having a control handle regulating the total discharge rate of water from the faucet, a thermostatically controlled valve, a temperature indicator, and a selectively disengagable stop limiting the maximum hot water temperature setting wherein the valve, the indicator and the stop are each mounted within the control handle.